Normal-appearing grey and white matter T1 abnormality in early relapsing–remitting multiple sclerosis: a longitudinal study

Objective

To investigate the presence and evolution of T1 relaxation time abnormalities in normal-appearing white matter (NAWM) and grey matter (GM), early in the course of relapsing–remitting multiple sclerosis (MS).

Methods

Twenty-three patients with early relapsing–remitting MS and 14 healthy controls were imaged six monthly for up to three years. Mean follow-up was 26 months for MS patients and 24 months for controls. Dual-echo fast-spin echo and gradient-echo proton-density and T1-weighted data sets (permitting the calculation of a T1 map) were acquired in all subjects. GM and NAWM T1 histograms were produced and a hierarchical regression model was used to investigate changes in T1 over time.

Results

At baseline, significant patient-control differences were seen, both in NAWM (P = 0.001) and in GM (P = 0.01). At follow-up, there was no evidence for a serial change in either mean T1 or peak-location for either NAWM or GM. There was weak evidence for a decline in patient NAWM peak-height and also evidence for a decline in control GM peak-height.

Conclusion

There are significant and persistent abnormalities of NAWM and GM T1 in early relapsing-remitting MS. Further studies should address whether such T1 measures have a role in prognosis or therapeutic monitoring. Multiple Sclerosis 2007; 13:169–177. http://msj.sagepub.com

Studies of the Deposition of Sub-Micron Particles on Turbine Blades

The paper describes the continuation of work to evaluate the magnitude of diffusional deposition of small particles on turbine blades. Apparatus and techniques similar to those described in an earlier paper have been employed. Modifications were necessary to overcome the problem of electrostatic charging of the deposition surface affecting the deposition results. Test results for the distribution of deposited particles around the blade have been obtained for three mass median diameters of 0·13, 0·19 and 0·24 μm and the influence of the level of turbulence at inlet to the cascade assessed. A theoretical treatment is derived which satisfactorily predicts the experimental results for the case of low inlet turbulence level.

The paper also gives details of the technique, using electron microscopy, of obtaining size distribution data for the minute particles.

Visible Photonic Band Gap Waveguide Devices

Photonic band gap (PBG) structures are multidimensional lattices, formed by a strong modulation of dielectric constant which prevent the propagation of photons over a forbidden energy range1. Since the first demonstration of a PBG at microwave frequencies2-7, it has proved technologically difficult to create a PBG in the optical region of the spectrum8-11 since the band gap centre wavelength is of the order of twice the lattice pitch. Recently, we have succeeded in fabricating novel waveguide designs which incorporate a TE polarised visible photonic band gap12,13 By reducing the band gap to visible wavelengths, we greatly simplify the experimental investigation of the behaviour of these complicated structures.

In this paper, we present the fabrication and initial optical testing of devices with band gaps in the visible wavelength range 545nm-632.8nm. These devices demonstrate unusual optical effects dependent upon the number of lattice periods such as: broadband wavelength filtering, wavelength dependent beam splitting, and broadband polarisation selective routing. In contrast to the well known active applications of PBGs, we suggest a host of new passive applications for PBGs in optical computing and wavelength division multiplexed (WDM) communications.

Phase I and DCE-MRI evaluation of CDP791, a di-Fab PEG conjugate that inhibits VEGFR2

3523

Background: VEGF inhibitors are of proven clinical value. However, very few drugs specifically inhibit VEGFR2. CDP791 is a di-Fab PEG conjugate that binds VEGFR2 with a Kd of 49pM. Methods: We performed a single site, open label, dose-escalation study of CDP791. Cohorts of patients received between 0.3 and 30 mg/kg every 3 weeks until disease progression. DCE-MRI was performed at each dose level. Results: Thirty-one patients with colorectal, ovarian or renal cancer or other tumors were treated. There was no observed dose limiting toxicity or maximum tolerated dose. At doses of 10mg/kg or above, 7/16 patients developed cutaneous hemangiomata that regressed upon drug withdrawal. Biopsy of these confirmed that CDP791 was co-located with unphosphorylated VEGFR2. DCE-MRI revealed a dose- dependent inhibition of tumor growth over 20 days post-treatment, although there was no measurable change in Ktrans, an indicator of blood flow and capillary permeability. Fourteen patients received extended treatment and 5 (with renal (x2), colorectal, endometrial cancer and melanoma) had stable disease after 6 cycles. Plasma concentrations of CDP791 >10mcg/mL were sustained across the 21-day cycle for doses 10mg/kg and above. Conclusions: CDP791 is a pure VEGFR2 antagonist that is well tolerated up to doses of 30mg/kg. The drug is mechanistically active, associated with hemangiomata and dose-level dependent inhibition of tumor growth but not with reduction in vascular permeability or blood flow on DCE-MRI. These data imply that the drug is active in patients but challenge our understanding of the regulation of tumor vascular permeability. In addition, they suggest that serial 3-dimensional measurements of short-term tumor growth patterns are a sensitive method to detect biological therapy-related tumor growth inhibition.

[Table: see text]

Highly engineered mesoporous structures for optical processing

Arranging periodic, or quasi-periodic, regions of differing refractive index in one, two, or three dimensions can form a unique class of mesoporous structures. These structures are generally known as photonic crystals, or photonic quasicrystals, and they are the optical analogue of semiconducting materials. Whereas a semiconductor's band structure arises from the interaction of electron or hole waves with an arrangement of ion cores, the photonic crystal band structure results from the interaction of light waves with an arrangement of regions of differing refractive index. What makes photonic crystals highly attractive to the optical engineer is that we can actually place the regions of differing refractive index in a pattern specifically tailored to produce a given optical function, such as an extremely high dispersion, for example. That is, we can define the geometrical arrangement of the dielectric foam to provide us with the form of band structure we require for our optical functionality. In this paper, the optical properties and applications of these highly engineered mesoporous dielectrics will be discussed.

Slow light and chromatic temporal dispersion in photonic crystal waveguides using femtosecond time of flight

We report time-of-flight experiments on photonic-crystal waveguide structures using optical Kerr gating of a femtosecond white-light supercontinuum. These photonic-crystal structures, based on engineered silicon-nitride slab waveguides, possess broadband low-loss guiding properties, allowing the group velocity dispersion of optical pulses to be directly tracked as a function of wavelength. This dispersion is shown to be radically disrupted by the spectral band gaps associated with the photonic-crystal periodicity. Increased time-of-flight effects, or "slowed light," are clearly observed at the edges of band gaps in agreement with two-dimensional plane-wave theoretical models of group velocity dispersion. A universal model for slow light in such photonic crystals is proposed, which shows that slow light is controlled predominantly by the detuning from, and the size of, the photonic band gaps. Slowed light observed up to time delays of approximately 1 ps, corresponds to anomalous dispersion of approximately 3.5 ps/nm per mm of the photonic crystal structure. From the decreasing intensity of time-gated slow light as a function of time delay, we estimate the characteristic losses of modes which are guided in the spectral proximity of the photonic band gaps.

Time-resolved measurement of propagating spin waves in ferromagnetic thin films

We measure the propagation of spatially localized spin waves in NiFe thin films through local inductive detection of the dynamic magnetization. A pulsed magnetic field excites a linear superposition of spin wave modes with a distribution that is predominantly driven by the spatial dependence of the in-plane excitation field. The results of numerical micromagnetic calculations exhibit excellent agreement with experiment and show that a comprehensive account of spatial nonuniformity and propagation is necessary to accurately measure the intrinsic damping rate.

Quantification of spinal cord atrophy from magnetic resonance images via a B-spline active surface model

A method is presented that aims at segmenting and measuring the surface of the spinal cord from MR images in order to detect and quantify atrophy. A semiautomatic segmentation with very little intervention from an operator is proposed. It is based on the optimization of a B-spline active surface. The method allows for the computation of orthogonal cross-sections at any level along the cord, from which measurements are derived, such as cross-sectional area or curvature. An evaluation of the accuracy and reproducibility of the method is presented.

Accurate multislice gradient echo T(1) measurement in the presence of non-ideal RF pulse shape and RF field nonuniformity

A methodology is presented for estimating T(1) using a two-point technique with a standard multislice gradient echo sequence. The method explicitly corrects for the shape of the RF pulse and for spatial variations in transmitted RF field intensity. Including these factors in the calculation of T(1) gives a substantial improvement in accuracy and precision of two-point gradient echo T(1) measurements in the presence of RF nonuniformity and non-ideal pulse profiles. The mean accuracy of the technique was found to be 1.4%. The mean precision was found to be 3.0%. The mean variation along the axis of a head coil was found to be 2.3%.

Investigation of MS normal-appearing brain using diffusion tensor MRI with clinical correlations

OBJECTIVE

To quantitatively investigate water diffusion changes in normal-appearing white matter (NAWM) and gray matter in patients with MS, and to evaluate whether these changes are correlated with clinical disability and disease duration.

BACKGROUND

Diffusion tensor imaging provides quantitative information about the magnitude and directionality (anisotropy) of water diffusion in vivo and detects pathologic changes in MS brain tissue.

METHODS

Diffusion tensor imaging was performed in 39 patients with MS and in 21 age-matched control subjects. Quantitative indices, including fractional anisotropy, volume ratio, and mean diffusivity, were obtained in 30 regions of interest located in normal-appearing basal ganglia, cerebellar gray matter, and supratentorial and infratentorial NAWM.

RESULTS

Patients with MS showed significantly reduced anisotropy and a trend toward increased diffusivity in the infratentorial and supratentorial NAWM, and significantly increased anisotropy in the basal ganglia. In all patients with MS, both fractional anisotropy and mean diffusivity in the cerebral peduncles were inversely correlated with the Expanded Disability Status Scale and pyramidal functional scores. In patients with relapsing-remitting MS, there was a strong correlation between Expanded Disability Status Scale score and fractional anisotropy in both supratentorial and infratentorial NAWM. In primary and secondary progressive MS, disease duration correlated strongly with mean diffusivity in infratentorial NAWM and fractional anisotropy in the cerebral peduncles, respectively.

CONCLUSION

The most striking finding of decreased fractional anisotropy in supratentorial and infratentorial NAWM and increased fractional anisotropy in basal ganglia may result from axonal degeneration due to fiber transection in remote focal lesions. Diffusion tensor imaging indices, in particular fractional anisotropy, appear sensitive to structural damage in NAWM that is associated with disability and progression in MS.

Combined functional magnetic resonance imaging and diffusion tensor imaging demonstrate widespread modified organisation in malformation of cortical development

A patient with a mild left hemiparesis and a malformation of cortical development in the right hemisphere was investigated with fMRI (functional magnetic resonance imaging) and DTI (diffusion tensor imaging). The motor cortex was studied using a finger tapping fMRI experiment. The fibre orientation was studied by displaying the principal eigenvector of the diffusion tensor in the spatially normalised brain of the patient and of control subjects. In addition, the anisotropy (directionality) of water diffusion of the patient was statistically compared with control subjects. The malformation was located in the right central region in the expected position of the motor cortex. fMRI showed activation anterior and posterior to the malformation. DTI disclosed that fibres with rostrocaudal orientation, presumably representing the pyramidal tract, were deviating from their normal orientation and passing around the malformation. There were widespread regions of reduced anisotropy affecting both hemispheres. In conclusion, fMRI and DTI provided concordant information showing widespread modified functional and structural organisation including regions which appeared normal on standard imaging.

Dynamic O-glycosylation of nuclear and cytosolic proteins: cloning and characterization of a neutral, cytosolic beta-N-acetylglucosaminidase from human brain

Dynamic modification of cytoplasmic and nuclear proteins by O-linked N-acetylglucosamine (O-GlcNAc) on Ser/Thr residues is ubiquitous in higher eukaryotes and is analogous to protein phosphorylation. The enzyme for the addition of this modification, O-GlcNAc transferase, has been cloned from several species. Here, we have cloned a human brain O-GlcNAcase that cleaves O-GlcNAc off proteins. The cloned cDNA encodes a polypeptide of 916 amino acids with a predicted molecular mass of 103 kDa and a pI value of 4.63, but the protein migrates as a 130-kDa band on SDS-polyacrylamide gel electrophoresis. The cloned O-GlcNAcase has a pH optimum of 5.5-7.0 and is inhibited by GlcNAc but not by GalNAc. p-Nitrophenyl (pNP)-beta-GlcNAc, but not pNP-beta-GalNAc or pNP-alpha-GlcNAc, is a substrate. The cloned enzyme cleaves GlcNAc, but not GalNAc, from glycopeptides. Cell fractionation suggests that the overexpressed protein is mostly localized in the cytoplasm. It therefore has all the expected characteristics of O-GlcNAcase and is distinct from lysosomal hexosaminidases. Northern blots show that the transcript is expressed in every human tissue examined but is the highest in the brain, placenta, and pancreas. An understanding of O-GlcNAc dynamics and O-GlcNAcase may be key to elucidating the relationships between O-phosphate and O-GlcNAc and to the understanding of the molecular mechanisms of diseases such as diabetes, cancer, and neurodegeneration.

Optical trirefringence in photonic crystal waveguides

We demonstrate that 2D photonic crystals can possess optical trirefringence in which there are six field orientations for which linear incident light is not perturbed on reflection or transmission. Such a property is rigorously forbidden in homogeneous nonmagnetic dielectrics which can possess only optical birefringence. We experimentally demonstrate this phenomena in silicon-based mesostructures formed from photonic crystal waveguides embedded in a Fabry-Perot cavity. Multirefringence is controlled by the presence of submicron dielectric patterning and is well explained by an exact scattering matrix theory.

Preliminary evidence for neuronal damage in cortical grey matter and normal appearing white matter in short duration relapsing-remitting multiple sclerosis: a quantitative MR spectroscopic imaging study

Neuronal damage and loss is likely to underlie irreversible disability in multiple sclerosis (MS). The time of onset, location and extent of neuronal damage in early disease are all uncertain. To explore this issue 16 patients with short duration, mild relapsing-remitting disease (mean disease duration 1.8 years, median EDSS 1) were studied using short echo time proton magnetic resonance spectroscopic imaging (1H-MRSI) to quantify the concentration of the neuronal marker N-acetyl-aspartate (NAA). The data were compared with those from 12 age-matched controls. 1H-MRSI was obtained from a 1.5-cm-thick slice just above the lateral ventricles. The Linear Combination (LC) Model combined with locally developed software allowed automated measurement of absolute metabolite concentrations from lesions, normal-appearing white matter (NAWM) and cortical grey matter (CGM). MS CGM exhibited significantly lower NAA (P = 0.01) and myo-inositol (P = 0.04) than control CGM. MS NAWM exhibited a lower concentration of NAA (P = 0.01) and increased myo-inositol (P = 0.03) than control white matter. More marked reductions in NAA and increases in myo-inositol were seen in lesions. The reduced NAA in MS CGM and NAWM suggest that mild but widespread neuronal dysfunction or loss occurs early in the course of relapsing-remitting MS. This preliminary finding should be confirmed in a larger cohort, and follow-up studies are also needed to determine the prognostic and pathophysiological significance of these early changes.

Effects of androgen deprivation on prostatic morphology and vascular permeability evaluated with mr imaging

PURPOSE

To assess magnetic resonance (MR) measures of vascular permeability of prostate cancer treated with androgen deprivation and to correlate these with morphologic appearances and serum prostate-specific antigen (PSA) levels.

MATERIALS AND METHODS

MR examinations in 56 consecutive patients with prostate cancer were performed before and after luteinizing hormone-releasing hormone analog treatment. T2-weighted and contrast medium-enhanced T1-weighted MR images were obtained. Pre- and posttreatment comparisons of morphologic features, glandular volume, and enhancement-related parameters (capillary permeability, leakage space, gadolinium accumulation) were made.

RESULTS

Fifty-five tumors were seen before treatment; 42, after treatment. Signal intensity in the peripheral zone and seminal vesicles decreased on T2-weighted images in 42 (75%) and 25 (45%) patients, respectively. Median volume in tumor decreased by 65% (95% CI: 55%, 76%); in central gland, by 30% (95% CI: 25%, 35%). Reductions in tumor permeability (P <.001) and changes in washout patterns were observed (P <.001). Tumor permeability reductions coincided with a decrease in serum PSA levels in 91% of patients. A weak correlation between tumor permeability and volume change was seen (r = 0.55, P =.04). Reductions in peripheral zone (P <.001) and central gland (P =.009) permeability were noted.

CONCLUSION

Androgen deprivation decreases tumor volume and vascular permeability and impairs detection of prostate cancers. Use of MR estimates of permeability may be an additional way of assessing prostatic tumor response to antiandrogen treatment.

Streptozotocin-induced beta-cell death is independent of its inhibition of O-GlcNAcase in pancreatic Min6 cells

Streptozotocin (STZ) injection into experimental animals selectively causes massive beta-cell death. The mechanism of this specific toxicity is not fully understood. Recently, it has been discovered that O-linked N-acetylglucosamine (O-GlcNAc) is enriched in the beta-cells. It has been proposed that STZ toxicity may be due to its inhibition of neutral O-GlcNAcase activity, the enzyme that removes O-GlcNAc from cytosolic proteins (K. Liu et al., 2000, Proc. Natl. Acad. Sci. USA 97, 2820-2825). To further ascertain the role of O-GlcNAcase in beta-cell death, we have used PUGNAc, a potent and specific O-GlcNAcase inhibitor, together with STZ in pancreatic Min6 cells. Both STZ and PUGNAc increased O-GlcNAc to similar levels on intracellular proteins. STZ, but not PUGNAc, decreased cellular protein synthesis by 66.0% within 8 h, killed 80.9% of the cells within 18 h, and decreased insulin secretion. STZ, but not PUGNAc, also caused genomic DNA fragmentation, suggesting that some of the cells were undergoing apoptosis. Prolonged treatment with PUGNAc (72 h) maintained high intracellular O-GlcNAc levels, but did not result in any apparent cell damage. Furthermore, the toxicity of STZ can be largely reversed by 3-aminobenzamide, a poly(ADP-ribose) polymerase inhibitor. These data strongly indicate that STZ-induced beta-cell death is not caused by elevated intracellular O-GlcNAc levels, but instead likely involves poly(ADP-ribose) polymerase in the mechanism.

MTR and T1 provide complementary information in MS NAWM, but not in lesions

MTR and T1 relaxation times are abnormal in MS lesions and NAWM, and may reflect tissue damage such as demyelination and axonal loss. Their relationship and potential to provide complementary information in tissue characterisation is explored. The aim of this study was to document the relationship between magnetisation transfer ratio (MTR) and T1 relaxation time in Multiple Sclerosis (MS) lesions and normal appearing white matter (NAWM) in order to determine whether the combination provides a more comprehensive tissue characterisation than either parameter in isolation. Ten patients with relapsing remitting MS and 10 age matched healthy controls underwent imaging using a protocol which included the measurement of both MTR and T1 relaxation times. The MTR and T1 values were compared statistically using a commonly adopted correlation approach and a mixed-model regression approach. There was a strong correlation between MTR and T1 in MS lesions (r=0.74). The correlation was seen equally in T1 hypointense and isointense lesions. The relationship was much weaker in MS NAWM (r=0.24) and no correlation was found in control white matter (r=0.06). Mixed-model regression analysis confirmed that the relationship between T1 and MTR is strongly dependent upon tissue type (MS lesion, MS NAWM, or control white matter). The relationship between MTR and T1 relaxation time measurements varies markedly between pathological and normal tissue types. In MS, the complementary information obtained from MTR and T1 is most apparent in NAWM. The results emphasise the potential for combinations of MR parameters to improve tissue characterisation, which in turn should improve understanding of disease pathology and treatment monitoring. Multiple Sclerosis (2000) 6 327 - 331

Variations in T1 and T2 relaxation times of normal appearing white matter and lesions in multiple sclerosis

OBJECTIVE

To investigate the variation in T1 and T2 relaxation times of normal appearing white matter (NAWM) and lesions in multiple sclerosis (MS) throughout the brain.

BACKGROUND

The magnetic resonance imaging (MRI) sequence fast FLAIR (fluid attenuated inversion recovery) has demonstrated overall increased lesion detection when compared to conventional or fast spin echo (FSE) but fewer lesions in the posterior fossa and spinal cord. The reasons for this are unknown, but may be due to variations in the T1 and T2 relaxation times within NAWM and MS lesions.

METHOD

Ten patients and 10 controls underwent MRI of the brain which involved FSE, fast FLAIR and the measurement of T1 and T2 relaxation times.

RESULTS

Of 151 lesions analysed (22 infra-tentorial, 129 supra-tentorial), eight were missed by the fast FLAIR sequence. T1 and T2 relaxation times in normal controls were longer in the infra-tentorial, than supra-tentorial, region. Patient NAWM relaxation times were prolonged compared with control values in both regions. Lesions demonstrated longer relaxation times than either control white matter or patient NAWM in both regions, however this difference was less marked infra-tentorially. The eight posterior fossa lesions not visible on the fast FLAIR sequence were characterised by short T1 and T2 relaxation times which overlapped with the patient NAWM for both T1 and T2 and with control values for T2 relaxation times.

CONCLUSION

Both lesion and NAWM relaxation time characteristics vary throughout the brain. The T1 and T2 relaxation times of infra-tentorial lesions are closer to the relaxation times of local NAWM than supra-tentorial lesions, resulting in reduced contrast between posterior fossa lesions and the background NAWM. Consequently the characteristics of some lesions overlap with those of NAWM resulting in reduced conspicuity. By utilising this information, it may be possible to optimise fast FLAIR sequences to improve infra-tentorial lesion detection.

Magnetic resonance imaging screening in women at genetic risk of breast cancer: imaging and analysis protocol for the UK multicentre study. UK MRI Breast Screening Study Advisory Group

The imaging and analysis protocol of the UK multicentre study of magnetic resonance imaging (MRI) as a method of screening for breast cancer in women at genetic risk is described. The study will compare the sensitivity and specificity of contrast-enhanced MRI with two-view x-ray mammography. Approximately 500 women below the age of 50 at high genetic risk of breast cancer will be recruited per year for three years, with annual MRI and x-ray mammography continuing for up to 5 years. A symptomatic cohort will be measured in the first year to ensure consistent reporting between centres. The MRI examination comprises a high-sensitivity three-dimensional contrast-enhanced assessment, followed by a high-specificity contrast-enhanced study in equivocal cases. Multiparametric analysis will encompass morphological assessment, the kinetics of contrast agent uptake and determination of quantitative pharmacokinetic parameters. Retrospective analysis will identify the most specific indicators of malignancy. Sensitivity and specificity, together with diagnostic performance, diagnostic impact and therapeutic impact will be assessed with reference to pathology, follow-up and changes in diagnostic certainty and therapeutic decisions. Mammography, lesion localisation, pathology and cytology will be performed in accordance with the UK NHS Breast Screening Programme quality assurance standards. Similar standards of quality assurance will be applied for MR measurements and evaluation.

Diffusion tensor imaging can detect and quantify corticospinal tract degeneration after stroke

Diffusion tensor imaging (DTI) fully characterises water molecule mobility in vivo, allowing an exploration of fibre tract integrity and orientation in the human brain. Using DTI this study demonstrates reduced fibre coherence (anisotropy) associated with cerebral infarction and in the corticospinal tract remote from the lesion, in five patients 2 to 6 months after ischaemic stroke. The study highlights the potential of DTI to detect and monitor the structural degeneration of fibre pathways, which may provide a better understanding of the pattern of clinical evolution after stroke.

In vivo 1H-magnetic resonance spectroscopy of the spinal cord in humans

Magnetic resonance spectroscopy (MRS) has been used in a variety of conditions affecting the central nervous system. Until now, only the brain has been studied, and spectroscopy of the spinal cord has not been previously reported. During the past 12 months, we have been experimenting with MRS of the cervical spinal cord of healthy volunteers. We present this technique, its current limitations, and possible future technological improvements and potential applications.

Nonlinear smoothing for reduction of systematic and random errors in diffusion tensor imaging

Calculation and sorting of the eigenvectors of diffusion using diffusion tensor imaging has previously been shown to be sensitive to noise levels in the acquired data. This sensitivity manifests as random and systematic errors in the diffusion eigenvalues and derived parameters such as indices of anisotropy. An optimized application of nonlinear smoothing techniques to diffusion data prior to calculation of the diffusion tensor is shown to reduce both random and systematic errors, while causing little blurring of anatomical structures. Conversely, filtering applied to calculated images of fractional anisotropy is shown to fail in reducing systematic errors and in recovering anatomical detail. Using both real and simulated brain data sets, it is demonstrated that this approach has the potential to allow acquisition of data that would otherwise be too noisy to be of use.

Test liquids for quantitative MRI measurements of self-diffusion coefficient in vivo

A range of liquids suitable as quality control test objects for measuring the accuracy of clinical MRI diffusion sequences (both apparent diffusion coefficient and tensor) has been identified and characterized. The self-diffusion coefficients for 15 liquids (3 cyclic alkanes: cyclohexane to cyclooctane, 9 n-alkanes: n-octane to n-hexadecane, and 3 n-alcohols: ethanol to 1-propanol were measured at 15-30 degrees C using an NMR spectrometer. Values at 22 degrees C range from 0.36 to 2.2 10(-9) m(2)s(-1). Typical 95% confidence limits are +/-2%. Temperature coefficients are 1.7-3.2% degrees C. T1 and T2 values at 1.5 T and proton density are given. n-tridecane has a diffusion coefficient close to that of normal white matter. The longer n-alkanes may be useful T2 standards. Measurements from a spin-echo MRI sequence agreed to within 2%.

A (1)H magnetic resonance spectroscopy study of aging in parietal white matter: implications for trials in multiple sclerosis

1H magnetic resonance spectroscopy (MRS) provides a unique tool to detect and quantify brain metabolites. In multiple sclerosis it can be used to investigate axonal loss or dysfunction through measurement of N-acetyl aspartate (NAA), a neuronal marker. Previous studies in adults have reported variable effects of aging on metabolite concentrations but have predominantly focused on changes in the elderly. This study has examined a younger adult age group to provide a reference database more applicable to the multiple sclerosis population. Single voxel (1)H MRS was carried out in 44 subjects between 22 and 62 years of age. Sixteen subjects underwent repeat examination after one year. Absolute concentrations of NA (the sum of NAA and N-acetyl aspartate glutamate), NAA, creatine/phosphocreatine (Cr), choline containing compounds (Cho) and myo-inositol (mI) were measured. NA, NAA and mI concentrations did not correlate with age but there were significant correlations between age and Cr (r = 0.43, p = 0.004) and Cho (r = 0.38, p = 0. 011) concentrations. No significant differences in metabolite concentrations were seen over one year. This study provides evidence that age-related changes of metabolite concentrations occur even in a young to middle aged adult population. This emphasizes the need to perform absolute quantification of metabolite concentrations rather than ratios and the importance of age-matching in (1)H MRS studies of multiple sclerosis.

Lesion heterogeneity in multiple sclerosis: a study of the relations between appearances on T1 weighted images, T1 relaxation times, and metabolite concentrations

OBJECTIVES

Multiple sclerosis lesions appear as areas of high signal on T2 weighted MRI. A proportion of these lesions, when viewed on T1 weighted MRI, appear hypointense compared with surrounding white matter. These hypointense T1 lesions are thought to represent areas of greater tissue damage compared with the more non-specific, total T2 lesion load. This study aimed to better characterise the properties of high signal T2 lesions with differing appearances on T1 weighted MRI using quantitative MR techniques.

METHODS

Eleven patients with secondary progressive multiple sclerosis were studied. Two high signal T2 lesions were selected from each patient-one of which appeared hypointense and one isointense on a T1 weighted image. A voxel was positioned around each lesion and for this volume of brain the metabolite concentrations were estimated using proton MR spectroscopy ((1)H-MRS) and the T1 relaxation time within each voxel calculated from a T1 map generated using a multislice technique.

RESULTS

Compared with isointense T1 lesions, hypointense T1 lesions exhibited a significantly lower absolute concentration of N-acetyl derived metabolites (tNAA) and a significantly higher absolute concentration of myo-inositol (Ins). T1 relaxation time correlated significantly with both tNAA (r=-0.8, p < 0.001) and Ins (r=0.5, p=0. 012). There was no correlation between T1 relaxation times and creatine/phosphocreatine or choline containing compounds.

CONCLUSIONS

Prolonged T1 relaxation times seem to reflect the severity of axonal damage or dysfunction (inferred by a low tNAA) and possibly also gliosis (inferred by a high Ins) in chronic multiple sclerosis lesions.

Development of high throughput screening assays using fluorescence polarization: nuclear receptor-ligand-binding and kinase/phosphatase assays

Fluorescence polarization (FP) has been used to develop high throughput screening (HTS) assays for nuclear receptor-ligand displacement and kinase inhibition. FP is a solution-based, homogeneous technique requiring no immobilization or separation of reaction components. The FP-based estrogen receptor (ER) assay is based on the competition of fluorescein-labeled estradiol and estrogen-like compounds for binding to ER. These studies determined the Kd for this interaction to be 3 nM for ERalpha and 2 nM for ERbeta; IC50 values for 17beta-estradiol, tamoxifen, 4-OH-tamoxifen, and diethylstibestrol were determined to be 5.6, 189, 26, and 3.5 nM, respectively. In a screen of 50 lead compounds from a transcriptional activation screen, 21 compounds had IC50 values below 10 microM, with one having an almost 100-fold higher affinity for ERbeta over ERalpha. These data show that an FP-based competitive binding assay can be used to screen diverse compounds with a broad range of binding affinities for ERs. The FP-based protein-tyrosine kinase (PTK) assay uses fluorescein-labeled phosphopeptides bound to anti-phosphotyrosine antibodies. Phosphopeptides generated by a kinase compete for this binding. In c-Src kinase reactions, polarization decreased with time as reaction products displaced the fluorescein-labeled phosphopeptide from the anti-phosphotyrosine antibodies. The experimentally determined IC50 of AG 1478 was 400 pM, while Genistein did not inhibit the epidermal growth factor receptor at similar concentrations. Like the FP-based PTK assay, the protein kinase C (PKC) assay utilizes competition. PKC isoforms had different turnover rates for the peptide substrate. The IC50 for staurosporine was less than 10 nM for all PKC isoforms. Tyrosine phosphatase assays use direct binding rather than competition. Increasing concentrations of T-cell protein-tyrosine phosphatase (TC PTP) increased the rate of dephosphorylation. This change in polarization was dependent on TC PTP and was inhibited by 50 microM Na3VO4. The IC50 of Na3VO4 was 4 nM for TC PTP. These data demonstrate that a FP-based assay can detect kinase and phosphatase activity. Homogeneous, fluorescent techniques such as FP are now methods of choice for screening many types of drug targets. New HTS instrumentation and assay methods like these make FP a technology easily incorporated into HTS.

Diffusion tensor imaging demonstrates deviation of fibres in normal appearing white matter adjacent to a brain tumour

The objective was to study fibre orientation in the cerebral white matter of a patient with a brain tumour using diffusion tensor imaging (DTI). A patient with a mild left hemiparesis and a tumour in the right frontal lobe and 20 healthy volunteers were scanned with a DTI sequence. The scans were spatially normalised and the fibre orientation in the patient compared with the fibre orientation in normal controls. DTI disclosed a change of the orientation of fibres in the patient compared with normal controls. In the normal appearing white matter adjacent to the tumour fibres deviated from the normal superior inferior orientation in the corona radiata by about 30 degrees. This finding was consistent with a displacement by distant mass effect rather than a destruction of fibres, in agreement with the neurological examination. In conclusion, DTI demonstrated a deviation of fibres in normal appearing white matter adjacent to a tumour. The technique will improve understanding of the effects of structural abnormalities on fibres. This will assist the interpretation of clinical findings and functional imaging studies and guide neurosurgical interventions.

Test liquids for quantitative MRI measurements of self-diffusion coefficient in vivo

A range of liquids suitable as quality control test objects for measuring the accuracy of clinical MRI diffusion sequences (both apparent diffusion coefficient and tensor) has been identified and characterized. The self-diffusion coefficients for 15 liquids (3 cyclic alkanes: cyclohexane to cyclooctane, 9 n-alkanes: n-octane to n-hexadecane, and 3 n-alcohols: ethanol to 1-propanol were measured at 15-30 degrees C using an NMR spectrometer. Values at 22 degrees C range from 0.36 to 2.2 10(-9) m(2)s(-1). Typical 95% confidence limits are +/-2%. Temperature coefficients are 1.7-3.2% degrees C. T1 and T2 values at 1.5 T and proton density are given. n-tridecane has a diffusion coefficient close to that of normal white matter. The longer n-alkanes may be useful T2 standards. Measurements from a spin-echo MRI sequence agreed to within 2%.

Improving image quality and T(1) measurements using saturation recovery turboFLASH with an approximate K-space normalisation filter

We present a method for reducing the image point-spread function and measuring T(1) using saturation recovery turboFLASH (SRTF) with centric-ordered k-space and a k-space correction filter designed to compensate for longitudinal magnetisation evolution during image acquisition. The method provides a two point T(1) measurement that reduces inaccuracies and image artefacts caused by longitudinal magnetisation evolution in conventional turboFLASH methods. The method is designed for use in rapid, quantitative measurements of contrast agent uptake in vivo.

Dynamic contrast enhanced MRI of prostate cancer: correlation with morphology and tumour stage, histological grade and PSA

AIM

To quantify MRI enhancement characteristics of normal and abnormal prostatic tissues and to correlate these with tumour stage, histological grade and tumour markers.

MATERIALS AND METHODS

Quantitative gradient recalled echo MR images were obtained following bolus injection of gadopentetate dimeglumine in 48 patients with prostate cancer. Turbo spin-echo T2-weighted images at the same anatomical position were reviewed for the presence of tumours (45 regions), normal peripheral zone (33 regions), and normal appearing central gland (30 regions). Time-signal intensity parameters (onset time, mean gradient and maximal amplitude of enhancement and wash-out score) and modelling parameters (permeability surface area product, lesion leakage space and maximum gadolinium concentration) were correlated with tumour stage, histological grade (Gleason score) and serum prostatic specific antigen (PSA) levels.

RESULTS

Significant differences were noted between peripheral zone and tumour with respect to signal intensity and modelling parameters (P = 0.0001), except onset time. No differences between central gland and tumour enhancement values were seen. There was weak correlation between MRI tumour stage and tumour vascular permeability (r(2) = 12%; P = 0.02) and maximum tumour gadolinium concentration (r(2) = 14%; P = 0.015). However, no significant correlations were seen with Gleason score or PSA levels.

CONCLUSION

Quantification of MR contrast enhancement characteristics allows tissue discrimination in prostate cancer consistent with known variations in microvessel density estimates.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

1H magnetic resonance spectroscopy of normal appearing white matter in primary progressive multiple sclerosis

Recent magnetic resonance imaging (MRI) and pathological studies have indicated that axonal loss is a major contributor to disease progression in multiple sclerosis. 1H magnetic resonance spectroscopy (MRS), through measurement of N-acetyl aspartate (NAA), a neuronal marker, provides a unique tool to investigate this. Patients with primary progressive multiple sclerosis have few lesions on conventional MRI, suggesting that changes in normal appearing white matter (NAWM), such as axonal loss, may be particularly relevant to disease progression in this group. To test this hypothesis NAWM was studied with MRS, measuring the concentration of N-acetyl derived groups (NA, the sum of NAA and N-acetyl aspartyl glutamate). Single-voxel MRS using a water-suppressed PRESS sequence was carried out in 24 patients with primary progressive multiple sclerosis and in 16 age-matched controls. Ratios of metabolite to creatine concentration (Cr) were calculated in all subjects, and absolute concentrations were measured in 18 patients and all controls. NA/Cr (median 1.40, range 0.86-1.91) was significantly lower in NAWM in patients than in controls (median 1.70, range 1.27-2.14; P = 0.006), as was the absolute concentration of NA (patients, median 6.90 mM, range 4.62-10.38 mM; controls, median 7.77 mM, range 6.60-9.71 mM; P = 0.032). There was no significant difference in the absolute concentration of creatine between the groups. This study supports the hypothesis that axonal loss occurs in NAWM in primary progressive multiple sclerosis and may well be a mechanism for disease progression in this group.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

Wallerian degeneration in the optic radiation after temporal lobectomy demonstrated in vivo with diffusion tensor imaging

PURPOSE

Diffusion tensor imaging allows the quantitative assessment of the microstructural organization of tracts in vivo (MR tractography). We used the new technique of MR tractography to demonstrate the effects of temporal lobectomy on the optic radiation.

METHODS

Spatially normalised maps encoding magnitude of the bias (anisotropy) of diffusion of three patients with temporal lobe resections were compared with spatially normalised diffusion maps of 22 control subjects. All three patients were operated on for the treatment of medically intractable temporal lobe epilepsy and had a normal neurologic examination before surgery. One patient had an amygdalocorticectomy. Two patients had standard en bloc resections, one of whom developed a homonymous hemianopia after surgery.

RESULTS

In the patient with hemianopia, a significant reduction of diffusion anisotropy (greater than mean+/-2 SD) consistent with wallerian degeneration was demonstrated in the optic radiation on the side of the temporal lobectomy, extending from the temporal to the occipital lobe. In the other patient with standard en bloc resection but clinically no hemianopia, the optic radiation was only marginally affected. In the third patient (amygdalocorticectomy), the diffusion anisotropy was within the normal range in the expected position of the optic radiation.

CONCLUSIONS

Our findings show that MR tractography may be a useful tool to demonstrate wallerian degeneration in the optic radiation after temporal lobectomy in patients with hemianopia. This is the first time that this new method has been applied in postoperative imaging; it enables us to visualise the morphologic correlate of dysfunctional pathways after epilepsy surgery in vivo. The potential for using MR tractography to study other aspects of epilepsy is discussed.

Proton MR spectroscopy in clinically isolated syndromes suggestive of multiple sclerosis

The concentration of the metabolite N-acetyl aspartate (NAA), thought to be a marker of axonal loss or damage, has been shown to be reduced in lesions, as demonstrated by high signal areas on T2-weighted MRI, and in normal-appearing white matter (NAWM) in established multiple sclerosis (MS). The stage of the disease when these changes first appear is not known. To try to determine this we studied 20 patients with clinically isolated syndromes, many of whom will be at the earliest clinical stages of MS, and 20 age- and sex-matched controls with single-voxel proton magnetic spectroscopy (MRS). MRS was performed using a General Electric 1.5T Signa EchoSpeed scanner (TR 3000 ms, TE 30 ms, PRESS). Absolute metabolite concentrations were determined using the LCModel fitting software. No significant reduction of NAA concentration was evident in the NAWM of the patients (patients: median 7.3 mM; controls: median 7.7 mM; P=0.19). There was, however, a significantly lower concentration of NAA in lesions (median 6.6 mM, P=0.015). Absolute values of choline-containing compounds, creatine and myo-inositol were significantly raised in the lesions (P=0.007, P=0.011 and P=0.002 respectively). The low NAA in lesions is consistent with axonal loss, damage or dysfunction occurring focally at the earliest clinical phase of the disease. The lack of any significant reduction in NAA in patient NAWM demonstrates that more widespread axonal changes are not yet detectable at this early clinical stage. A larger cohort and follow-up will be necessary to determine whether or not MRS findings have any prognostic significance for individual patients or sub-groups. This will also enable the clarification of the time course, pathogenesis and pathophysiological significance of the development of the low NAA, which is found in the NAWM of many patients with established MS.

Reproducibility of magnetic resonance imaging measurements of spinal cord atrophy: the role of quality assurance

A sensitive magnetic resonance imaging (MRI) method to measure spinal cord cross-sectional area with the potential to monitor disease progression has recently been developed. As changes in cord area due to disease are usually small, assessment of the reliability of the methodology is essential in serial studies of spinal cord atrophy. The aim of this study was to institute and evaluate a protocol of quality assurance to determine long-term reproducibility of serial studies. Serial MRI of the spinal cord was carried out in five healthy volunteer controls over 1 year. Cross-sectional spinal cord areas were measured in a total of 46 scans. The mean coefficient of variation of all subjects over one year was 1.35%. The intra-observer coefficient of variation for same scan analysis was 0.63%. This study has confirmed high reliability of our serial data over one year and the on-going quality assurance protocol enables continuing evaluation of the reproducibility of results in serial studies. Quality assurance is an essential and practical component of all serial MRI studies, without which the clinical implications of change cannot be reliably evaluated.

Pharmacokinetic analysis of neoplasms using contrast-enhanced dynamic magnetic resonance imaging

Pharmacokinetic analysis using dynamic magnetic resonance imaging provides insight into various physiological aspects of tumors, including capillary wall permeability and the volume of the interstitial space. This physiology may be investigated in either a heuristic or model-based fashion using various methods presented in the literature. This review describes many of these approaches and provides some guidelines for those intending to use dynamic magnetic resonance imaging in the investigation of neoplasms.

Short echo time single-voxel 1H magnetic resonance spectroscopy in magnetic resonance imaging-negative temporal lobe epilepsy: different biochemical profile compared with hippocampal sclerosis

Single-voxel proton magnetic resonance spectroscopy (1H MRS) has shown abnormalities in patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS). Many TLE patients, however, do not have HS or other lesions on quantitative magnetic resonance imaging (MRI) (MRI-negative). Fifteen control subjects, 15 patients with unilateral HS, and 15 MRI-negative TLE patients underwent 1H MRS at an echo time of 30 msec on a 1.5-T GE Signa scanner. Voxels were tailored to the individual hippocampi. N-Acetylaspartate (NAA), creatine, choline, total glutamate plus glutamine (Glx), and myo-inositol (Ins) were quantitated by using an external standard and LCModel, a user-independent quantitation method. Normal ranges were defined as the control mean +/- 2.5 SD. In HS patients, 12 of 15 had abnormally low NAA in sclerotic hippocampi; 3 of these 12 also had abnormally low NAA contralaterally. Abnormally low NAA/Ins ratios lateralized the side affected by HS in 7 of 15 patients, without any bilateral abnormalities. In 15 MRI-negative TLE patients, 4 had abnormally low hippocampal NAA ipsilateral to seizure onset, 1 of whom had abnormally low NAA bilaterally. Analysis of groups of subjects showed a bilateral decrease in NAA, most marked in patients with HS and on the side of seizure onset. The mean NAA/Ins ratio was lower in patients with HS than in control subjects and in MRI-negative patients. The concentration of Glx was higher ipsilateral to seizure onset in MRI-negative patients than in HS patients. Quantitative short echo time 1H MRS identified abnormalities in 87% of patients with HS and 27% of MRI-negative TLE patients in concordance with other lateralizing data. In individual and group comparisons, 1H MRS described a metabolite profile in the hippocampi of MRI-negative TLE patients that was different from patients with HS, with an increase in Glx and a less marked decrease in NAA than was seen in HS.

A direct demonstration of both structure and function in the visual system: combining diffusion tensor imaging with functional magnetic resonance imaging

The relationships between functional activation patterns and the structural properties of brain pathways have not been widely studied. The recently developed magnetic resonance imaging technique of diffusion tensor imaging (DTI) allows a full characterization of water molecule mobility in three dimensions, providing new structural information that is not available from other in vivo imaging techniques. The directional bias of diffusion (anisotropy) may be derived from the diffusion tensor, and is related to fiber tract integrity and orientation. Since DTI and functional magnetic resonance imaging (fMRI) both require rapid (generally echoplanar) imaging it is possible to obtain geometrically matched images from the two modalities. fMRI and DTI were combined in a visual system study using photic stimulation to demonstrate the feasibility of combining the two methods and to investigate the structural properties of activated regions compared to the white matter tracts. Blood oxygenation level-dependent (BOLD) fMRI activation maps were directly overlayed upon fractional anisotropy (FA) maps, avoiding registration and spatial transformation by carefully matching acquisition parameters. Activated regions had lower FA than optic radiation white matter, supporting the hypothesis that most BOLD signal change occurs within the relatively isotropic cortical grey matter. The combination of these modalities in future studies may provide further insights into relationships between brain structure and function in both health and disease.

The structural and functional mechanisms of motor recovery: complementary use of diffusion tensor and functional magnetic resonance imaging in a traumatic injury of the internal capsule

OBJECTIVES

Recovery from focal motor pathway lesions may be associated with a functional reorganisation of cortical motor areas. Previous studies of the relation between structural brain damage and the functional consequences have employed MRI and CT, which provide limited structural information. The recent development of diffusion tensor imaging (DTI) now provides quantitative measures of fibre tract integrity and orientation. The objective was to use DTI and functional MRI (fMRI) to determine the mechanisms underlying the excellent recovery found after a penetrating injury to the right capsular region.

METHODS

DTI and fMRI were performed on the patient described; DTI was performed on five normal controls.

RESULTS

The injury resulted in a left hemiplegia which resolved fully over several weeks. When studied 18 months later there was no pyramidal weakness, a mild hemidystonia, and sensory disturbance. fMRI activation maps showed contralateral primary and supplementary motor cortex activation during tapping of each hand; smaller ipsilateral primary motor areas were activated by the recovered hand only. DTI disclosed preserved structural integrity and orientation in the posterior capsular limb by contrast with the disrupted structure in the anterior limb on the injured side.

CONCLUSIONS

The findings suggest that the main recovery mechanism was a preservation of the integrity and orientation of pyramidal tract fibres. The fMRI studies do not suggest substantial reorganisation of the motor cortex, although ipsilateral pathways may have contributed to the recovery. The initial deficit was probably due to reversible local factors including oedema and mass effect; permanent damage to fibre tracts in the anterior capsular limb may account for the persistent sensory deficit. This study shows for the first time the potential value of combining fMRI and DTI together to investigate mechanisms of recovery and persistent deficit in an individual patient.

The effect of section thickness on MR lesion detection and quantification in multiple sclerosis

BACKGROUND AND PURPOSE

The purpose of our study was to investigate the effect of section thickness on MR detection of brain lesion volume and measurement precision in patients with multiple sclerosis (MS).

METHODS

Eight subjects with known MS were studied on a 1.5-T MR system. We used a 3D fast fluid-attenuated inversion-recovery sequence to obtain contiguous axial brain images at section thicknesses of 5 mm, 3 mm, and 1 mm. Two sets of images were acquired at each section thickness during two sessions, between which the patient was removed from the scanner. Lesion volumes were measured at each section thickness using a semiautomated local thresholding technique.

RESULTS

We found that progressive reduction in section thickness led to detection of smaller lesions, resulting in a significant (8%) increase in lesion volume on MR images as section thickness was reduced from 5 mm to 3 mm. However, despite a further increase in lesion detection at a section thickness of 1 mm, this did not result in an increase in total lesion volume. This finding indicates that the relationship between section thickness and lesion volume on MR images is not linear. Scan-rescan reproducibility was improved by reducing section thickness, at the cost of increased analysis time.

CONCLUSION

This study shows that acquisition of very thin sections increases the sensitivity and precision of MS lesion measurement. Serial studies assessing lesion changes over time are needed to define the impact of this increase on sample size requirements for MS treatment trials.

Spinal cord atrophy and disability in MS: a longitudinal study

OBJECTIVE

To assess whether it is possible to measure changes in cord cross-sectional area during a 1-year period in patients with MS reliably.

BACKGROUND

Involvement of the spinal cord in MS is extremely common and an important element in the development of disability. Although little relation has been shown between the cord lesion load and disability, a strong correlation between spinal cord atrophy and the expanded disability status scale (EDSS) has been demonstrated in cross-sectional studies.

METHOD

A highly reproducible semiautomated technique that measures the cross-sectional area of the cord at the C2 level was applied to 13 healthy control subjects and 28 patients serially.

RESULTS

This study confirms that patients have significantly smaller cords than control subjects at baseline (control subjects: mean 80.95 mm2, patients: mean 71.25 mm2, p = 0.01) and demonstrates that patients have a significant loss in cord cross-sectional area during 12 months, which was not seen in control subjects (p < 0.001). This reduction in cord size was most marked in the primary progressive patients who had a mean cord cross-sectional area loss of 3.52 mm2 (5.2%) and least in the secondary progressive (-0.26 mm2, 0.7%) and benign patients (-0.41 mm2, 0.8%). The baseline cord cross-sectional area correlated strongly with the EDSS (r = -0.52, p = 0.005) and with disease duration (r = -0.75, p < 0.001); however, there was no significant difference in cord area (p = 0.69) or change in cord area (p = 0.51) between those patients with a definite increase in EDSS and those without.

CONCLUSION

This study demonstrates, for the first time, that it is possible to measure changes in cord cross-sectional area over time. The serial measurement of spinal cord atrophy may thus make an important contribution to the evaluation of therapeutic efficacy, especially in primary progressive disease.